Fire resistant closure for passageways



Feb. 7, 1967 w. A. BEAR FIRE RESlSTANT CLOSURE FOR PASSAGEWAYS 3Sheets-Sheet l Filed Feb. 28, 1964 Will/'am A. Bear n, Q IV I 30 20 4434 36 I Io JN VIIN'I'UK Y @m WW awel,

Feb. 7, 1967 w. A. BEAR 4 3,302,343

FIRE RESISTANT CLOSURE FOR PASSAGEWAYS Filed Feb. 28, 1964 3Sheets-Sheet 2 fig. 5

a! Will/'am A. Bear INI/liNI/'OK Feb. 7, 1967 w. A.BEAR

FIRE RESISTANT CLOSURE FOR PASSAGEWAYS Filed Feb,v 28, 1964 Fig. .9

Wil/iam A. Bear INVHN'IUR. ma

I BY @uw Attorneys 3,302,343 Patented Feb. 7, 1967 hee 3 302,343 FIRERESISTANT CLSUREFOR PASSAGEWAYS William A. Bear, Bear Coal Co.,Somerset, Colo. 81434 Filed Feb. 28, 1964, Ser. No. 348,177 8 Claims.(Cl. 52-98) 'Ilhe present invention generally relates to "a tireIesistant closure for passageways and while the invention isspecifically adapted for use in coal mines, it Iwill have other uses andapplications wherein a lire resistant closure is desirable.

In mining operations `and especially in coal mines, certain tunnels,cross-cuts and other .passageways must be closed in =an air-tight'manner to control the flow of air for safety purposes in removingharmful gases and for providing fresh air as well as for lire control.In present procedures, this `air-tight closure is often accomplished bybuilding masonry walls similar to those used in building structures, Itwill be `appreciated that the building of such a masonry wall is quitetime-consuming :and requires the services of a mason and also requiresthat the building material for the wall be conveyed to the point ofconstruction of the air-tight closure which requires considera-ble timeand effort.

Accordingly, it is -an object of the present invention to provide `afire resistant closure for underground passageways such as tunnels,`cross-cuts and the like appearing in a coal mine or lany other minewhich is constructed of a fabricated metal framework having fireresistant material mounted thereon so that the framework components maybe standard manufactured `articles thereby reducing the cost of assemblyand enabling assembly in a shop or other area located above ground.

Another objection to the masonry wall for forming a closure for `a minepassageway is the fact that such a closure is substantially permanent inthat the wall or closure cannot be removed except by using implementsnormally employed for tearing down a maconry wall. Therefore, it is afurther object of the present invention to provide a fire resistantclosure including stripping means incorporated therein for enabling thefireresistant closure to be easily removed by miners or the like whendesired or necessary such as in an emergency condition such as whenendeavoring to escape from one tunnel into another in lche event of anexplosion, accumulation of gas or the like.

Still another object of the present invention is to provide a lireresistant closure that may be equipped with anchoring prongs in order tohold the closure in position in the passageway thereby enabling theiclosure to be set up securely without waiting for mortar to dry such asoccurs in constructing a masonry wall. Also, when the closure of thepresent invention is removed, the components thereof may be re-usedWhereas a masonry structure when it is broken up cannot be re-used.

A further object of the present invention is to provide a fire resistantclosure for the ground passageways having a prefabricated framestructure with screen paneling and a foam plastic material lappliedthereto which is lire resistant and also capable of being sealed aroundthe edges of the passageway by spraying the foam material into anyopening around t-he periphery of the closure due to irregularities inthe surface of the passageway.

Still another object of the present invention is to provide a reresistant closure which is rather simple in construction, easy toinstall, advantageous as compared with a conventional masonry wall and`relatie/ely inexpensive to manufacture.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of `construction andoperation as more yfully hereinafter described and claimed, referencebeing had to the raecornpanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIGURE 1 is an elevational View of the fire resistant closure of thepresent invention installed in an underground passageway;

FIGURE 2 is a top plan view of the `construction of FIGURE 1;

FIGURE 3 is a detailed elevational view of the re resistant closure withthe layered components thereof broken away for illustrating theconstruction of the framework, the screen panelling 'and the foammaterial thereof;

FIGURE 4 is a vertic-al, sectional view, on an enlarged scale, takensubstantially upon a plane passing along section line 4-4 of FIGURE lillustrating further structural details o-f the re resistant closure ofthe present invention;

FIGURE 5 is a detailed sectional View, on an enlarged scale, takensubstantially upon a plane passing along section line 5-5 of FIGURE 3illustrating further structural details of the invention;

FIGURE 6 is an elevational View, portions broken away, illustratinganother embodiment of the invention orientated in an irregularly shapedpassageway;

FIGURE 7 is an elevational view illustrating another embodiment of theinvention with portions thereof broken away illustrating the manner inwhich a door may be incorporated into the fire resistant closure;

FIGURE 8 is a fragmental perspective view of one corner of a frameworkillustrating the manner in which prongs may be used for securing theclosure in place;

FIGURE 9 is a plan view of a closure assembly illustrating the manner inwhich the panels thereof may be overlapped vfor forming a completeclosure for the passageway;

FIGURE 10 is a perspective view illustrating :a prefabricated panel suchas used in the assembly of FIG- URE 9;

FIGURE 11 is a lperspective view illustrating the manner of forming thepanel of FIGURE 10;

FIGURE 12 is -a sectional view taken substantially upon a plane passing:along section line 12-12 of FIG- URE l-l illustrating furtherstructural details of the manner of forming the panel of FIGURE 10;

FIGURE 13 illustrates one form of connecting means between components ofthe framework for enabling adjustment and dismantling thereof;

FIGURE 14 is a perspective View of the fastener employed in FIGURE 13;and

FIGURE 15 is a fragmental perspective view illustrating one manner offorming fastener elements on the framework for suspending the screenpanelling therefrom.

Referring now specifically to the drawings, the numeral 10 generallydesignates the closure of the present invention installed in a cross-cutpassageway 12 interconnecting tunnels 14 for forming a closure for thepassageway 12. The passageway 12 is substantially rectangular in configJuration and the lire resistant closure 10 includes an adjustablerectangular framework I6 including longitudinally adjustable end membersI8 and longitudinally adjustable longitudinal members 20. Each of theend members 18 are constructed of a pair of angle iron members 22 and 24each of which is provided with a plurality of longitudinally spacedapertures 26 therein by virtue of which the overlapping ends thereof maybe secured adjustably together by a pair of fastening members 28 whichmay be conveniently nut and bolts or the like. As illustrated, theapertures 26 in one of the members 22 are slightly elongatedlongitudinally while the apertures 26 in the other of the members 2d areslightly elongated trans- E versely thus enabling a certain degree ofmisalignment of the angle iron members 22 and 24 in order to conform theend members I3 to the side walls of the passageway I2.

The longitudinal rails or members are also constructed of a pair ofangle iron members and 32 which overlap in the same adjustable mannerwith each of the members being provided with apertures 34 for receivingfasteners 36 with the apertures 34 being orientated in the same manneras in the end member I8. The upper and lower longitudinal members 20 aresecured to the end members 18 by fastening bolts 38 at the ends of theend members 18 and an intermediate longitudinal member 20 is securedadjustably to either of the sections 24 or Z2 by a suitable fasteningbolt 40.

For anchoring the frame I6 to the top and bottom wall of the passageway,anchoring elements 42 are inserted through apertures provided in thehorizontal flanges of the sections of the longitudinal members Ztl. Theanchoring members 42 may be any suitable type of expansion device whichmay be driven into the top wall of the passageway or it may be the typeof device that requires a pre-drilled hole.

Attached to the vertical or outer ange of the angle iron members 30 and32 which forms the top longitudinal member Ztl is a plurality ofgenerally L-shaped hooks 44 secured rigidly to the flange of the angleiron members 30 and 32 as illustrated in FIGURE 4. A screen paneling 46of reticulated screen material is supported from the framework by'engaging over the hooks 44 as illustrated in FIGURE 4 therebydetachably supporting the screen panels 46 on the framework I6.

Mounted on and impregnated through the openings of the screen panels 46is a coating or layer of foamed plastic material 48 which is fireresistant and which forms a complete closure for the screen panelings 46and the framework 16. The foam plastic 48 is sprayed on and around theedges of the framework between the irregularities in the passageway 12and the framework I6, the foam plastic is sprayed into the openings asindicated by numeral 50 in FIGURE 4 thus completely sealing in anairtight manner the passageway 12. The foam plastic mav terial issprayed in place by conventional methods and any suitable foam plastichaving rire resistant properties may be employed. One example of suchfoam which may be effectively employed is sold under the name of RigidFoam7 by Mine Safety Appliance Company.

With the layer of foam plastic material laminated to the screenpanelling I6, a continuous monolithic closure is provided for thepassageway l2. Incorporated into the structure is a means for enablingremoval thereof and this means includes a plurality of stripping wires52 which are embedded in the foam plastic material immediately jadjacent the surface of the screen panelling 46 as illustrated in FIGURE4 and also in FIGURE 5. The top j end of the stripping wire 52 projectsforwardly from the face of the foam material 48 so that by gripping thefree end thereof, the stripping wire may be pulled downwardly thusforming a kerf or groove substantially completely through the foamplastic material whereby the screen panelling 46 may then be removed bylifting it upwardly off of the hooks 44 thereby enabling the closure tobe removed in the event of an emergency or in the event it is desired toremove the closure for any reason whatsoever. The bottom ends of thestripping Wire 52 are fastened to the screen panels by twisting the wirethereto at the bottom edge of the screen panel. It is pointed out thatthe stripping wire 5?; must be lined up with the edges of the screenwire panel so that they coincide whereby the foam will be completely cutthrough when the stripping wire is pulled at the loose end thus breakingthe bond at the panel joints so that the panels may be removed andsalvaged when changing air stops and in case of an emergency a trappedminer can pull a few wires, remove the panels and escape providing he ison the foam side of the closure. If trapped on the frame side of theclosure, he merely kicks the panels apart by kicking at the screenpanels near a juncture between the panels.

As will be apparent, the framework is constructed of readily availablestructural components which may be easily transported to the site of theclosure and erected using conventional erecting procedures with noparticular skills required for installing the closure panel. After theframework has been set up, the screen panels may be easily assembledthereon and the stripping wires orientated in proper position and thefoam material sprayed thereon in a conventional manner thus forming acomplete air-tight closure for the passageway 12 in a relatively shorttime and using relatively unskilled labor and enabling the dismantlingof the closure for re-use of the components when desired and enablingemergency exit of a trapped miner or the like in the event it becomesnecessary to remove the closure for this purpose.

FIGURES 6 and 7 illustrate other types of installations which may beemployed. FIGURE 6 illustrates a generally trapezoidal arrangementincluding a framework 54 which may be constructed in the same generalmanner as the above invention but with the lower longitudinal framemember being longer than the intermediate longitudinal frame member andthe upper longitudinal frame member thus enabling one of the end framemembers 56 to be lorientated. in an angular relation or inclinedrelation to conform generally to the surface of the passageway 58. Inthis form of the invention, the screen panels 60 are applied in the samemanner with one of the screen panels being of irregular shape tocompletely overlie the framework 54 and the stripping wires are appliedin the same manner along with the foam plastic material.

In FIGURE 7, the framework 62 is constructed of conventional angle ironcomponents and includes a door frame structure receiving and pivotallysupporting a door 64 that is constructed `of the same type of componentsas employed in the framework and supported from the door frame by hinges66 and a suitable handle 68 is provided for enabling the door to beopened and closed when desired. In this construction, the door as wellas the framework is provided with screen panelling 68 of overlappingsections and the foam plastic covers a screen panelling on the door aswell as the screen panelling on the framework 62 thus providing aclosure panel having an access door therethrough which may be secured inclosed position by any suitable means. Stripping wires are provided inthis construction in the same manner as in the construction of FIGURESl-4 inasmuch as there is a possibility that the door will become jammedand it may become necessary to have an emergency eXit alongside of thedoor which may be accomplished by pulling the stripping wire in themanner described hereinbefore. Further, the stripping wires enables thescreen panels and the foam plastic thereon to be removed for dismantlingso that they can be re-used later on.

FIGURE 8 illustrates a framework 70 having an anchor means 72 connectedthereto in the form of an elongated rod '74 having an L-shaped bracket76 attached to the corner of the framework 70 by fastening bolts '78 orthe like. The rod 74 is welded in pl-ace as at 80 in perpendicularrelation to the framework '70 and the ends of the rod 74 each areupturned and provided with pointed terminal ends S2 for forming prongsfor anchoring the framework 7l) to the peripheral surface of thepassageway. The rod 74 provides resiliency to the anchor prongs and theprongs serve as supports for the framework thereby eliminating thenecessity of using the roof and floor anchors illustrated in FIGURESl-5.

FIGURES 9l2 disclose another type of closure generally designated bynumeral 84 orientated in a passageway 86. In this form of the invention,a plurality of prefabricated panels generally designated by 88 areemployed and are mounted on a framework 90 which includes overlappingadjustable longitudinal frame members 92 and overlapping adjustable endframe members 94 with their being provided supporting hooks or the likeon the vertical flange of the uppermost longitudinal frame member 92.Each of the prefabricated panels 88 includes a screen panelling member96 generally equivalent to the screen panels 46 employed in FIGURES 1-5.Applied to the screen panelling 96 is a layer of foam plastic material98 equivalent to the foam plastic material 48 employed in FIGURES 1-5.Also incorporated into the foam plastic material 98 is a stripping Wire100 that is embedded in the foam plastic material closely adjacent thescreen panelling 96 and closely adjacent one edge thereof. The panels 88are prefabricated and each of the panels 88 have a portion of the screenpanel 96 projecting laterally of the plastic material 98 so that thisflange or portion of the screen panel 96 may overlap under an adjacentedge of an adjacent panel 88 thus forming an overlapping connectionbetween the prefabricated panel 88 as illustrated in FIGURE 9. Thejoints between the panels 88 may be filled with a foam plastic material102 as illustrated in FIGURE 9 and the space between the periphery ofthe closure 84 and the passageway 86 may also be filled with foamplastic 104 thus forming a cornplete closure. In this form of theinvention, the panels are prefabricated and the frame 90 is installedand the panels merely hung in place thereon from the topmostlongitudinal frame members and with the panels 88 in overlappingrelation. Then, the joints 102 are sealed with the foam plastic 102 andthe periphery of the closure is sealed by the foam plastic 104 thusforming a quickly assembled closure and also provided an arrangement inwhich the panels may be readily disassembled by employing the strippingwire which due to its close proximity to the edge of the foam plastic 98having the seal foam plastic 102 engaged therewith will break the bondbetween the adjacent panel 88 by cutting through a very small portion ofthe foam plastic 98 and also the foam plastic 102 thereby breaking thebond between the panels 88 so that they may be removed to enabledismantling of the closure for re-use for the stripping wires enablingdismantling of the panels 88 to enable passage through the passageway 86in the event of an emergency.

FIGURES 11 and 12 illustrate a structure for forming the prefabricatedpanels 88 and include a supporting plate 106 having a narrow plate 108attached to one edge thereof by hinges 110. The plate 106 supports thescreen panelling 96 with the pivot plate 108 overlying a portion of theedge thereof for clamping the screen panel 96 in place and also forminga protector for the area of the screen panel 86 which will not becovered with the foam plastic 98. One end of the plate 106 is providedwith a bracket 112 having a notch 114 therein which receives one end ofthe stripping wire 100. The other end of the stripping wire is anchoredto the screen panel 96 at the opposite end thereof. After the screenpanel 96 has been assembled on the supporting plate 106 and thestripping wire 100 orientated therein, the foam plastic 98 .is appliedand allowed to harden. Spacer blocks 116 are provided along the edge ofthe plate 106 having the hinges 110 for properly orientating the screenpanel 96 in relation to the supporting plate 106. The top surface of theplate 106 which may be Wood or metal, is provided with a covering ofplastic sheeting 118 such as polyethylene or the like in order toprevent adhesion of the foam to the top surface of the supporting plate106.

The prefabricated panels 88 are formed above ground outside of the mineand enables the relatively inexpensive production of such panels andthen conveyance of the panels to an underground location therebyrequiring only the installation of a framework using conventionalstructural components at the underground site thereby reducing the costof the closure member and enable installation thereof with relativelyunskilled labor.

FIGURES 13 and 14 illustrate a manner of securing the frame memberstogether including fastener elements having tapered ends 122 forcentering the aligned apertures in frame sections 124 and 126. Each ofthe fasteners 120 is provided with a slot-like aperture 128 extendingtherethrough for receiving a wedge-type securing element which willserve not only to clamp the frame members 124 and 126 together but alsoserves to frictionally anchor itself in place as illustrated in FIGURE13.

FIGURE 14 illustrates a frame member 132 having a vertical flange 134with an outwardly struck upwardly inclined lug 136 which forms a hookfor supporting the screen panels which represents an optional manner offorming the supporting hooks for the screen panels along the top framemember of the closure.

The structural elements may be angle iron or other suitable shapes andmay be constructed of standard steel or aluminum structural sections orit may be formed from steel or aluminum flat strips. Aluminum is usedwhere the structures are to be handled frequently in order to lessen thework load in installing them. As pointed out, the structural shape ofthe various frame members may be Varied as long as they have sucientstructural strength and of a shape necessary to adapt itself to theconditions encountered as well as to the size of the openings. Thesupporting frame work is adjustable so that it may be worked into avariety of shapes to conform to the conguration of the passageway bylengthening or shortening the members as desired. The hooksforsupporting the screen panels may be stamped, welded or riveted intoplace and in lieu of the bolt type connectors, various connectors may beemployed for securing the structural components in adjusted position.For example, the fastener structure illustrated in FIGURES 13 and 14 maybe employed as well as other types of fasteners. By using variousstructural elements, the shape of the closure member may be varied toconform with various irregular passageway shapes and the structuralpieces can be bent to make curved edges and could be constructed toclose off the `completely round or oval-shaped tunnel if desired. Inaddition, panels can be assembled in such a manner in an open space soas to form four walls and a top thus making a re resistant room.

As the foam is sprayed onto the screen panels or sprayed to seal theprefabricated panels, the voids between the peripheral wall and theinterior surface of the passageway is effectively sealed as the foamexpands and hardens. Where access is maintained through the re resistantclosure for purposes of inspection, maintenance, escape-ways or thelike, the arrangement in which a door is installed may be provided. Theanchoring prongs may be used when roof bolts cannot be used and theanchoring prongs are used on the four corners of the framework and, ifnecessary, they can be used at spaced points across the top and bottommembers but in this case they should have vertical frame members alignedtherewith to hold the prong members securely against the coal or rock.Due to the construction of the prongs and brackets illustrated in FIGURE8, the prongs will absorb movement due to the heaving of the floor.

In some installations, the center longitudinal frame member may not benecessary and, in some installations, the bottom frame member may beomitted for economic reasons. In the construction illustrated in FIGURES9, 10 and 11, the prefabricated panels are constructed and stored in adesired place until they are ready for use thus reducing the lcost ofsuch panels.

The advantages of the present invention over cement masonry structuresor closures commonly referred to as a cinder block closure are quiteapparent.

The actual man-time used in the mine at the point of building the reresistant closure is much less than when building out of cement masonryunits. This is extremely important in an emergency when a closure ofthis new type of construction could be put up and completed in a fewhours, compared with a much longer time when building a cement masonryunit closure.

Anyone can put up a new type of closure while the construction of oneout of cement masonry units requires that at least the person laying theblocks be a skilled mason.

There is no mortar to be mixed and no error to make in the proportionsof cement, lime, sand, and water as in the cement masonry unitconstruction. The chemical foam can be obtained in portable spraycontainers, ready to use, with no mixing of ingredients.

Screen panels may be prefabricated outside the mine with unskilledlabor, thus reducing the cost of building a closure. Prefabricatedscreen panels may be stockpiled where convenient to use. This is likebuilding the wall in big pieces ahead of time, something that cannot bedone with cement masonry units.

In an emergency, anchoring prongs are used to hold the closure inposition, resulting in setting one up securely without waiting formortar to dry, drilling holes, etc.

In removing a closure, a cement masonry unit closure is broken up, andthe pieces are not re-usable, while with the new type of closure thepanels are removable and the framework can be completely dismantled andre-used.

Parts of the framework on the new type of closure are built withadjustable connections to adapt it to different sizes and shapes ofopenings, while the cement masonry units must be cut to fit.

Any gaps along the edges of Ithe framework of the new type of closureare readily closed by spraying with the foam, while the cement masonryunits must be cut to fit, then mortar must be troweled into theopenings.

This new type of closure may be used in any position, whereas one builtof cement masonry units must be built in a vertical plane only.

Should a man become trapped on the foam side of a new type of closure,he can either pull a few stripping wires, loosen several panels and stepthrough the closure, or he can cut the foam with a pocket knife along ascreen panel joint and after loosening several panels, step through theclosure to safety. With a cement masonry 'unit it is almost impossibleto break through, especially with the cement and gravel type of blocks.

Should a man become trapped on the framework side of the closure he can,with a few well aimed kicks, break the bond between screen panels,separate them, and walk through the closure.

The new type of closure is fire resistant, both the foam and the steel.It will withstand a high temperature for quite some time. Some cinderblocks used in cement masonry unit construction contain enough coke andcoal 4to ignite under ideal conditions.

Should the new type closure be damaged by high enough temperatures todestroy some of the foam, it can have a new coat of foam sprayed onagain as soon as the immediate source of heat is removed. This cannot bedone with cement masonry units since the heat causes a chemical reactionin the cement itself. In the lime of the mortar a calcination takesplace when subjected to high temperatures. Dehydration of the cement andaggregate occurs which will cause spalling of the surface, thusdestroying the blocks if it continues deep enough.

In the new type of closure, full strength is obtained within a fewminutes after spraying on of the foam. In the cement masonry unitconstruction, full strength is not obtained until the mortar sets upcompletely, which sometimes takes as long as 24 4to 36 hours.

In the event of an explosion, a cement masonry unit closure isdestroyed. The new type of closure may be bent, torn, or otherwisedamaged, but with a minimum of replacement parts can be reerected,sprayed with foam, and back into use within a few hours.

If a lioor heaves, la cement masonry unit closure will break up. Whenthe same oor heavesy with a new type closure, it can bend, absorbing thepressure. If placed with the anchor prongs, the prongs will bend,absorbing most of the pressure from the heave. Cracks in the foam may bere-sprayed to render it airtight immediately.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention asclaimed.

What is claimed as new is as follows:

1. In a mine passageway a ire resistant closure cornprising a frame, aplurality of prefabricated panels, each of said panels including ascreen panel, a layer of foam resinous material thereon, said screenpanel including a portion of one edge thereof free of plastic wherebythe prefabricated panels are overlapped in relation to each other, andsealing foam plastic material sealing the juncture between theprefabricated panels.

2. The structure as defined in claim 1 wherein said foam plasticmaterial is provided with a stripping wire embedded therein adjacent oneedge of the screen panel for breaking the bond between adjacent panels,said frame including support means for the prefabricated panels adjacentthe upper edge thereof.

3. The structure as defined in claim 2 wherein said support meansincludes an inwardly and upwardly struck hook-type lugs formed in theframe.

4. The structure as dened in claim 1 including a means for supportingthe screenl panel from said frame, said supporting means including ahook-like projection on the upper end of said frame whereby the screenpanel may engage the hook-like projection and be detached therefrom.

5. The structure as defined in claim 1 wherein said frame is adjustableand includes peripheral members constructed of overlapping sections, theoverlapping portions of said sections being provided with a plurality ofapertures, and fastening means extending through selected apertures andsecuring the members in adjusted position.

6. The structure as defined in claim 5 wherein said fastening means isin the form of a bolt assembly.

7. The structure as defined in claim 5 wherein said fastening means isin the form of a headed fastener having a slot therein, and a wedgeinserted into said slot for securing the members in adjusted position.

8. The structure as defined in claim 1 wherein stripping wires areembedded in the foam resin adjacent the screen panel for separating thefoam plastic along the junctures between the screen panels to enable thescreen panels to be dismantled from the frame.

References Cited by the Examiner UNITED STATES PATENTS 603,402 5/1898Kearns 52-632 719,191 1/1903 Collins 52-348 1,484,520 2/ 1924 Michod52-513 2,035,595 3/1936 Crowe 52432 2,087,867 7/1937 Balduf 52-3492,941,900 6/ 1960 Stranzf. 3,182,423 4/1965 Jennings 52-99 FOREIGNPATENTS 725,756 1955 Great Britain.

OTHER REFERENCES Plastering Industries, January 1961, page 18.

Industrial and Engineering Chemistry, September 1963, page 49.

FRANK L. ABBOTT, Primary Examiner.

JOHN E. MURTAGH, Examiner.

1. IN A MINE PASSAGEWAY A FIRE RESISTANT CLOSURE COMPRISING A FRAME, APLURALITY OF PREFABRICATED PANELS, EACH OF SAID PANELS INCLUDING ASCREEN PANEL, A LAYER OF FOAM RESINOUS MATERIAL THEREON, SAID SCREENPANEL INCLUDING A PORTION OF ONE EDGE THEREOF FREE OF PLASTIC WHEREBYTHE PREFABRICATED PANELS ARE OVERLAPPED IN RELATION TO EACH OTHER, ANDSEALING FOAM PLASTIC MATERIAL SEALING THE JUNCTURE BETWEEN THEPREFABRICATED PANELS.